This present application relates generally to systems and apparatus for controlling the operation of wind turbines. More specifically, but not by way of limitation, the present application relates to systems and apparatus pertaining to improved detection of and protection from electrical faults during the operation of wind turbines.
Wind turbines compete with traditional forms of electric power generation. As a result they depend on cost effective, reliable, as well as safe means for capturing wind energy and converting it into electrical energy that may be delivered to distant locations for usage. In general, medium voltage is used to collect electric power from the several connected wind turbines that make up a wind farm facility. A fused disconnect (or other current interrupting device) is typically used to disconnect the individual wind turbines from the other turbines within the facility. More particularly, a fused medium voltage disconnect is generally located between the medium voltage and the step-up transformer. In such systems, the fused disconnects typically are coordinated with wind turbine equipment short circuits.
However, many types of wind turbine faults exist that do not produce short circuits. Indeed, some short circuits produce very little fault current. In addition, some wind turbine electric faults cause temporary or short-lived high currents. These types of currents, however, are fairly typical in wind turbine applications because the maintenance of voltage in the systems requires wind turbines to provide high currents at times. As a result, wind turbine fuses are designed to allow for relatively high currents. This, of course, makes them poor at detecting faults that result in only moderately high currents conditions. These characteristics mean that, typically, the electrical system of wind turbines are ill-equipped at detecting faults that result in anything less than the current produced by a bolted fault.
As one of ordinary skill in the art will appreciate, delays in the detection or outright failure of detection can cause extensive equipment damage in wind turbines. As a result, improved systems and apparatus for detecting and disconnecting fault currents in wind turbine applications are needed. Such improved systems would be able to detect and disconnect various faults that produce fault currents below fuse interrupting currents and other potentially damaging faults.